Flight management assembly of an aircraft, of a transport aircraft in particular, and to a method of monitoring such a flight management assembly

A flight management assembly of an aircraft, the flight management assembly comprising two flight management systems, each of the flight management systems being configured for generating data comprising at least one trajectory and at least one prediction of a parameter of the aircraft, wherein one of the flight management systems is an active flight management system and another of the flight management systems is a passive flight management system, wherein the flight management assembly comprises a monitoring and backup unit, the monitoring and backup unit being configured for carrying out at least one monitoring of at least one of items of data generated by the active flight management system in order to verify if the item of data is valid, and wherein the flight management assembly is configured for carrying out, in case of validation of the monitored item of data, a synchronization of the monitoring and backup unit and of the passive flight management system, with data called synchronization data of the active flight management system.